Linux BSP - Network is unreachable error

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We are developing a product using Linux BSP on a ColdFire 5475.
I can send messages to specific IP addresses over UDP; however, when I
attempt to send broadcast messages, I get the following error:

            "Network is unreachable"

I have seen the same problem when I run our software on the "ColdFire Lite
Development Kit" board from Freescale.

Except for having a broadcast thread ( the udp_inquire_thread ), I have the
same code working correctly on my Linux PC ( running Fedora Core 4). Using
/sbin/ifconfig I have checked both my Linux PC and the development board (
Linux BSP on the ColdFire ). /sbin/ifconf shows the following for both:

        Bcast:          Mask:

On the development board (Linux BSP) I have two threads: udp_listen_thread
and udp_inquire_thread.

The udp_listen_thread creates a UDP socket, sets the BROADCAST option, binds
the socket, and then waits for receive data in a while(1) loop.

            int     udp_sock;
            int     on;
            socklen_t    optlen;
            socklen_t    addr_len;
            struct sockaddr_in    addr_host;

            udp_sock = socket( AF_INET, SOCK_DGRAM, 0 );

            on = 1;
            optlen = sizeof( on );
            setsockopt( udp_sock, SOL_SOCKET, SO_BROADCAST, &on, optlen );

            addr_len                               = sizeof( addr_host );
            addr_host.sin_family             = AF_INET;
            addr_host.sin_port                = htons( 18001 );
            addr_host.sin_addr.s_addr    = htonl( INADDR_ANY );

            bind( udp_sock, (struct sockaddr *) &addr_host, addr_len );

            while (1)
                  // Read Socket ===>          recvfrom( udp_sock, ... );

                  // Process Msg

The udp_inquire_thread sends a specific message out the UDP socket to get
info about other devices.

          socklen_t                addr_len;
          struct soctaddr_in    addr_clnt;

          // Building Inquire Message ( inquire_msg ) here.


          addr_len = sizeof( struct sockaddr_in );
          memset( &addr_clnt, 0, addr_len );
          addr_clnt.sin_family            = AF_INET;
          addr_clnt.sin_port               = htons( 18001 );
          addr_clnt.sin_addr.s_addr   = htonl( INADDR_BROADCAST );

          while (1)
               sleep (10);

               pthread_mutex_lock( &udp_mutex );
               if ( -1 == sendto( udp_sock, &inquire_msg, msg_len, 0,
(struct sockaddr *) &addr_clnt, addr_len ) )
                  perror( "sending datagram message" );                  //
<=== "Network is unreachable" is sent from here.
               pthread_mutex_unlock( &udp_mutex );

Does anybody have a solution to this problem?

Thanks for the help.


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